1. Field of the Invention
The present invention relates to a liquid crystal display device where a liquid crystal material is held between a pair of substrates. The invention relates also to a method of fabricating such a liquid crystal display device.
2. Description of the Related Art
In recent years, liquid crystal display devices have been used as display devices for use in personal computers, word processors, TV receivers, and so on by making use of their merits (i.e., they are thin, lightweight, and low power consumption). Also, they find extensive use as projection type displays.
Among them, active matrix liquid crystal display devices where switching devices are electrically connected with each of pixel electrodes have been earnestly researched and developed because good display images can be accomplished without crosstalk between adjacent pixels.
As an example, the structure of an active matrix liquid crystal display device of the transmissive type is next described briefly. In the active matrix liquid crystal display device, a liquid crystal material is sandwiched between an array substrate and a counter substrate via orientation films.
The array substrate comprises a glass substrate on which signal lines and scanning lines are arranged in rows and columns. Thin-film transistors (TFTs) are disposed as switching devices near the intersections of the signal and scanning lines. Pixel electrodes of ITO (indium tin oxide) and the signal lines are connected via the TFTs. Storage capacitor lines run substantially parallel to the scanning lines on the glass substrate. A dielectric film is interposed to form storage capacitor (Cs) between the adjacent storage capacitor lines and pixel electrodes.
The counter substrate comprises a glass substrate on which a matrix-like light-shielding film are formed. The light-shielding film shields the light through the area between the pixel electrodes and the signal and scannning lines, and shields the light towards the TFTs. The counter electrodes of ITO are deposited over the light-shielding film.
The manner in which the array substrate and counter substrate are aligned to each other and assembled into a liquid crystal display device by the prior art techniques is now described by referring to FIGS. 12-14. One conventional method is first described by referring to FIGS. 12 and 13. The array substrate and counter substrate, indicated by 1100 and 1300, respectively, are sawn from their larger original substrate. This kind of sawing operation is so carried out that an extra peripheral region 1800 is given to the surroundings of the final contour of each substrate. Alignment marks 1271, 1273 and 1371, 1373 have been previously put on the peripheral regions 1800 of the substrates 1100 and 1300, respectively. On each substrate sawn apart, the alignment marks 1271, 1273 or 1371, 1373 are normally located at diagonally opposite corners. When both substrates 1100 and 1300 are bonded together, the alignment marks are aligned, using cameras (1701, 1072) or like that. After the bonding, the peripheral regions 1800 of the substrates 1100 and 1300 are scribed and removed.
Another conventional method is next described by referring to FIG. 14. A counter substrate 1300 has outer dimensions sufficiently larger than its final outer dimensions. The counter substrate 1300 has two alignment marks 1271 and 1273 in its peripheral region 1800 that is located outside the final contour. An array substrate 1100 is cut into its final contour. After the counter substrate 1300 and the array substrate 1100 are bonded together via a sealant material, the unwanted peripheral region of the counter substrate is scribed and removed before or after injection of a liquid crystal material.
Since the array substrate 1100 includes a connector region 1295 around its display region 1290 to permit electrical connections with an external circuit, the array substrate 1100 are sufficiently larger in outer dimensions than the display region 1290. Therefore, sufficient degrees of freedom are given in placing the alignment marks 1371 and 1373 outside the display region of the array substrate 1100, the marks being used for alignment with the counter substrate 1300.
On the other hand, the counter substrate 1300 makes little difference in outer dimensions with the display region 1290 and, therefore, it is difficult to place outside the display region 1291 the marks 1371 and 1373 for alignment with the array substrate 1100.
With the prior art techniques, it is difficult to take plural counter substrates from a large-sized original substrate. Consequently, much material loss results and thus it is difficult to improve the productivity.